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This paper introduces a new scheme for the numerical computation involving shock waves. The essence of the scheme is to adaptively implement a conjugate low-pass filter to effectively remove the accumulated numerical errors produced by a set of high-pass filters. The advantages of using such an adaptive algorithm are its controllable accuracy, relatively low cost and easy implementation. Numerical examples in one and two space dimensions are presented to illustrate the proposed scheme. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article invites submissions for research papers about numerical methods in engineering.

Barlow was the first to propose a method to predict optimal stress recovery points in finite elements (FEs). Prathap proposed an alternative method that is based on the variational principle. The optimal points predicted by Prathap, called Prathap points in this paper, have been reported in the literature for linear, quadratic and cubic elements. Prathap points turn out to be the same as Barlow points for linear and quadratic bar elements but different for cubic bar element. Nevertheless, for all the three elements, Prathap points coincide with the reduced Gaussian integration points. In this paper, an alternative implementation of Prathap's best-fit method is used to compute Prathap points for higher-order (viz., 4–10th order) bar elements. The effectiveness of Prathap points as points of accurate stress recovery is verified by actual FE analysis for typical bar problems. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper promotes the development of a novel family of finite elements with smoothed strains, offering remarkable properties. In the smoothed finite element method (FEM), elements are divided into subcells. The strain at a point is defined as a weighted average of the standard strain field over a representative domain. This yields superconvergent stresses, both in regular and singular settings, as well as increased accuracy, with slightly lower computational cost than the standard FEM. The one-subcell version that does not exhibit volumetric locking yields more accurate stresses but less accurate displacements and is equivalent to a quasi-equilibrium FEM. It is also subject to instabilities. In the limit where the number of subcells goes to infinity, the standard FEM is recovered, which yields more accurate displacements and less accurate stresses. The specific contribution of this paper is to show that expressing the volumetric part of the strain field using a one-subcell formulation is sufficient to get rid of volumetric locking and increase the displacement accuracy compared with the standard FEM when the single subcell version is used to express both the volumetric and deviatoric parts of the strain. Selective integration also alleviates instabilities associated with the single subcell element, which are due to rank deficiency. Numerical examples on various compressible and incompressible linear elastic test cases show that high accuracy is retained compared with the standard FEM without increasing computational cost. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The phenomenon of failure by catastrophic crack propagation in structural materials poses problems of design and analysis in many fields of engineering. Cracks are present to some degree in all structures. They may exist as basic defects in the constituent materials or they may be induced in construction or during service life. Using the finite element method, a lot of papers deal with the calculation of stress intensity factors for two- and three-dimensional geometries containing cracks of different shapes under various loadings to elastic bodies. In order to increase the accuracy of the results, special elements have been used. They are described together with methods for calculating the stress intensity factors from the computed results. At the vicinity of a crack tip, the strains are not always small, but they may also be large. In this case, the J-integral can also be applied to characterize the cracks in elastic or elastic–plastic bodies. This paper describes the computation of the two-dimensional J-integral for large strains to elastic and elastic–plastic bodies and represents some numerical examples. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To circumvent the constraint in application of the conventional differential quadrature (DQ) method that the solution domain has to be a regular region, an interpolation-based local differential quadrature (LDQ) method is proposed in this paper. Instead of using regular nodes placed on mesh lines in the DQ method (DQM), irregularly distributed nodes are employed in the LDQ method. That is, any spatial derivative at a nodal point is approximated by a linear weighted sum of the functional values of irregularly distributed nodes in the local physical domain. The feature of the new approach lies in the fact that the weighting coefficients are determined by the quadrature rule over the irregularly distributed local supporting nodes with the aid of nodal interpolation techniques developed in the paper. Because of this distinctive feature, the LDQ method can be consistently applied to linear and nonlinear problems and is really a mesh-free method without the limitation in the solution domain of the conventional DQM. The effectiveness and efficiency of the method are validated by two simple numerical examples by solving boundary-value problems of a linear and a nonlinear partial differential equation. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, numerical investigation of airflow through a human upper airway is presented using an unstructured-based characteristic-based split (CBS) scheme. The CBS scheme used in the present study employs a fully explicit matrix-free solution procedure along with artificial compressibility. A one equation Spalrat–Allmaras (SA) turbulence model is employed to study low and moderate Reynolds number flows. A detailed discussion of the qualitative and quantitative results is presented. The results show a strong influence of the Reynolds number on the flow pattern and quantities of interest, pressure drop and wall shear stress. It is also apparent that SA model can be employed on unstructured meshes to predict the steady flow with good accuracy. Thus, the novelties of the present paper are: use of the unstructured mesh-based solution algorithm and the successful application of the SA model to a typical human upper airway. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper investigates numerically and experimentally the influence of initial geometric imperfections on the critical loads of initially stretched thick hyperelastic cylindrical shells under increasing uniform internal pressure. Imperfections in shells can have a global or local character. First, two types of local imperfections are considered: (1) a local axially symmetric imperfection in the form of a ring and (2) a small rectangular imperfection. The influence of the imperfection thickness, position and size are analysed in detail. Results show that the critical load decreases as the imperfections increase in size or thickness and as they move from the boundaries to the centre of the shell. The influence of multiple local imperfections is also studied in the present paper. Finally, the influence of global imperfections is considered with the imperfections described as a variation of the shell curvature in the axial direction. The results show that thick hyperelastic shells may be sensitive to local and global imperfections. In all cases the experimental results are in good agreement with the numerical ones, corroborating the conclusions. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The spatial oscillation of values in the consolidation analysis when using small time increments has been a common problem for most existing methods. In this paper, the numerical characteristics of a simple finite element formulation for 1-D consolidation analysis recently proposed by the authors have been examined in detail. This paper proves that the commonly encountered phenomenon of spatial oscillation due to small time increments does not occur in the simple finite element formulation. The criterion of minimum time step used in most existing methods can be eliminated at least for linear situations by using the simple formulation proposed by the authors. Thus, the consolidation analysis can be carried easily for many situations, such as the one involving a relatively impermeable clay layer sandwiched between sandy layers. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

By using the natural boundary reduction an overlapping domain decomposition method is designed to solve some exterior two-dimensional time-dependent parabolic problems. The governing equation is first discretized in time, leading to a sequence of boundary value problems with respect to time step in an unbounded domain. Then artificial boundaries are introduced. For each time level, an overlapping domain decomposition method, which is based on the natural boundary reduction, is constructed to solve the exterior elliptic boundary value problem on a two-dimensional domain. It is shown that the algorithm is equivalent to Schwarz alternating method. The convergence of this algorithm is given. The contraction factor for the exterior circular domain is also discussed. In the end of this paper, some numerical examples are presented, which illustrate the feasibility and the effectiveness of the proposed methods in this paper. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Finite elements for very short wave scattering problems have recently been developed by various authors. These have almost exclusively dealt with the Helmholtz equation. The elements have been very successful, in terms of drastic reductions of the number of degrees of freedom in the numerical model. However, most of these elements are not directly applicable to problems in which the wave speed is not constant, but varies with position. Many wave problems fall into this latter category. The present paper demonstrates how concepts used in ray tracing approaches, for problems with varying wave speed, such as wave refraction in coastal areas, can be borrowed and applied to the new types of elements. The paper gives no numerical results, but outlines how the method can be extended, in a relatively simple manner, to solve a much larger class of wave problems, of great interest. [ABSTRACT FROM AUTHOR]

In this paper, a hypersingular integral equation for curved cracks in plane elasticity is formulated and presented. This paper describes a new numerical technique for solution of deep curved cracks in plane elasticity. In this method, the crack curve length is taken as the co-ordinate in the hypersingular integral equation of the curved crack problems. The curved crack configuration maps on the real axis with interval (-a,a), where ‘2a’ is the arc length of the crack. The original hypersingular integral equation is converted into other hypersingular integral equation which is formulated on the curve length co-ordinate, or on (-a,a). The hypersingular integral equation is solved numerically. Numerical examples prove that higher efficiency has been achieved in the suggested method. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, the implementation of a 3-D parallel CFD code using the meshless method. Reproducing Kernel Particle Method (RKPM) is described. A novel procedure for implementing the essential boundary condition using the hierarchical enrichment method is presented. The Total Arbitrary Lagrangian Eulerian (ALE) formulations using Finite Element Method are developed and implemented in the parallel code. The flow past a cylinder problem served as examples throughout the paper. Both methods have shown promising results compared with analytical solution. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A simple method to satisfy the homogeneous boundary condition in the element-free Galerkin method is proposed in this paper. Effectiveness of the method is demonstrated, through free vibration problems of Timoshenko beams. Several case studies involving different slenderness ratios and end conditions are carried out. The results of the present study are compared with those obtained using classical Rayleigh–Ritz and conventional element-free Galerkin method wherein Lagrangian multipliers are employed to satisfy boundary conditions. Eventhough, a one-dimensional problem is considered in the present paper, the validity of the proposed method for the two-dimensional problems is demonstrated theoretically. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper investigates the relationship between the energy- and momentum-conserving time-integration scheme of Simo and Gonzalez (Papers—American Society of Mechanical Engineers—All Series, 1993; 93(4)) and a momentum-conserving time-integration scheme due to Betsch and Steinmann (Int. J. Numer. Meth. Engng 2000; 49: 599) for N-body problems. The schemes are shown to be identical if the potential energy of interaction between masses is a polynomial function of the distances between the masses, of degree two or lower. In addition, they are shown to recover the same relative equilibria. Copyright © 2002 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Dynamics response of systems to impact or loading may be effectively treated by direct integration. However, it is often difficult to select the time-step of integration properly, especially in the case where the system is badly stiff. Zhong presented an explicit direct integration scheme, HPD, for the homogeneous systems. This paper extends HPD scheme to analyse systems with loading or impact, through Fourier expansion and homogenizing the initial system. Compared with other methods, the new scheme named homogenized high-precision direct integration (HHPD) has a higher precision and wider application and is less time-consuming, and several examples in this paper show HHPD's effectiveness in engineering. Copyright © 2002 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, it is shown that the symmetric Galerkin boundary element formulation cannot be used in its standard form for multiple connected bodies. This is because the traction integral equation used for boundaries with Neuman boundary condition give non-unique solutions. While this fact is well known from the classical theory of integral equations, the problem has not been fully addressed in the literature related to symmetric Galerkin formulations. In this paper, the problem is reviewed and a general way to deal with it is proposed. The details of the numerical implementation are discussed and an example is solved to demonstrate the effectiveness of the proposed solution. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Logical identification covers a wide range of applications dealing with constrained transformation processes between internal and external models of sequential systems. In this paper, we consider the differential identification approach whose purpose is to measure the influence of minor modifications of the internal or external models of an existing system. This class of identification is dedicated to sensitivity analysis: learning, redesign, diagnosis, etc. Thus, it reveals all its interest for the study of systems which have to adapt themselves to an evolving environment. This paper presents an overall view of the different differential identification approaches and their corresponding applications. We will propose a new resolution technique based on genetic simulation. In a second paper, we will focus on some experiments performed with a genetic identification tool. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper reports an intercomparison of three second-order accurate reconstruction schemes to predict 2D steady-state compressible Euler and Navier–Stokes flows on unstructured meshes. The schemes comprise one monotone slope limiter (Barth and Jespersen, A1AA Paper 89-0366, 1989) and two approximately monotone methods: the slope limiter due to Venkatakrishnan and a data-dependent weighting least-squares procedure (Gooch, Journal of Computational Physics, 1997; 133:6–17). In addition to the 1D scalar wave problem, comparisons were performed under two inviscid test cases: a supersonic 10° ramp and a supersonic bump; and two viscous laminar compressible flow cases: the Blasius boundary layer and a double-throated nozzle. The data-dependent oscillatory behaviour is found to be dependent on a user-supplied constant. The three schemes are compared in terms of accuracy and computational efficiency. The results show that the data-dependent procedure always returns a numerical steady-state solution, more accurate than the ones returned by the slope limiters. Its use for Navier–Stokes flow calculations is recommended. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The idea of the paper is to present theoretical aspects and finite element method implementation of the sensitivity analysis in homogenization of linear elastic fibre composites by the use of effective modules homogenization approach. The deterministic sensitivity approach to the homogenization problem is presented in a general form for n-component composite and is illustrated in the example of two-dimensional fibre-reinforced periodic composite structure. The results of sensitivity analysis shown in the paper confirm the usefulness of the homogenization method to computational analysis of composite materials and may be successfully applied to numerical optimization of engineering composites and to their shape sensitivity studies. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a simplified formula that can be used to obtain the detailed heat transfer rate and temperature distribution on the surfaces of square and non-square cooling channels of a nozzle guide vane (NGV). Due to the three-dimensional shape of the internally cooling channels, the heat transfer rate can vary substantially between the different sides of the channels. This detailed heat flux and resulting temperature distribution on the walls are important to improve the design of the airfoil as well as to determine the expected usable life of the NGV. This detail heat transfer data is usually obtained by means of a complex three-dimensional simulation of the NGV configuration. Therefore, for design purposes, the heat transfer data on the channel surfaces is often assumed to be the average heat transfer rate on the channel walls. The average heat transfer rate can be obtained by using a simplified heat transfer equation, based on the average Reynolds number in the channel. The simplified formula presented in this paper can be used to obtain the detailed heat transfer rate and temperature distribution on the surfaces of square and non-square cooling channels of a nozzle guide vane (NGV). The simplified formula is based on results obtained from three-dimensional simulations of the heat transfer in the channels and was compared to simulated and experimental data over a range in flow rates and channel geometries. In general, it can be concluded that the formulation produces fast and accurate results over a wide range of applications. Copyright © 2000 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper considers the numerical solution of one-dimensional Stefan problems. The basic method used is the heat balance integral method (HBIM). The method is applied to one-phase melting/solidification problems. Both cylindrical and spherical geometries are considered and a special starting procedure is used for small times to overcome the singularity at t=0. The method can also deal with heat transfer problems with temperature-dependent thermal properties. Numerical results are obtained for both cylindrical and spherical geometries and conclusions are drawn. Full details of the special starting procedure for both cylindrical and spherical geometries are discussed in a companion paper, Part II. This includes the derivation of the systems of non-linear algebraic equations for the coefficients in the small time series. Copyright © 2000 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper describes a new technique to stabilize meshless methods used in conjunction with point-based integration. The method proposed is based on the finite increment calculus (FIC) concepts for convection-dominated problems. In this paper a finite increment gradient operator is defined in such a way that second-order derivatives are included. This operator is then used in the context of a variational formulation of an elliptic problem in order to define a stabilized numerical procedure. For simplicity, the Poisson equation will be used in this paper to illustrate the method, although more general elliptic problems can be equally treated. An eigenvalue analysis will be carried out in order to demonstrate that no mechanisms are present in the resulting equations. Finally, a simple example will illustrate the technique. Copyright © 2000 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A linear θ method is used in this paper to improve the stability of the standard time-domain BEM formulation. The time-stepping procedure is similar to that of the Wilson θ method; however, unlike in the FEM, where linear time variation of acceleration (for elastodynamic problems) is assumed, here linear time variation for both potential and flux (for scalar waves) is assumed in the time interval θΔt. A comparison between numerical results obtained from the standard formulation and from the linear θ method studied here shows the latter to be more stable than the former. The effect of varying θ for different values of time steps is also studied in this paper. Copyright © 1998 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The paper presents a general method of large strain determination over the deformed surface of a sheet metal stamping. It is demonstrated that the conventional degenerated shell element with two normal rotation degrees of freedom is not suitable for large deformation, especially when large element rotation is present. This inaccuracy is primarily caused by the fact that the displacement field description used in the degenerated shell element is only a first-order approximation with respect to the two rotation degrees of freedom, and is therefore suitable only for small rotation angles. The new method presented in this paper replaces the two rotation DOFs with three new degrees of freedom to describe the rotation of the surface normal so that the element deformation can be accurately described with no limitation on the amount of deformation and rotation involved. The advantages of this new method are: (i) a linear and accurate expression of the displacement field in terms of nodal DOFs is obtained; (ii) the formulation is easily incorporated into any existing degenerated shell elements; (iii) the strain calculation is accurate for any amount of element rigid body rotation; (iv) if the method is used in surface grid analysis, the algorithm will not only provide correct surface strains, but also their variation through the thickness direction, i.e. the bending deformation. © 1998 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The governing equation of an elastic prismatic shaft is the two-dimensional Poisson equation defined on the cross-sectional area of the shaft. In this paper, the differential quadrature method (DQM) is employed to solve the Poisson equation on some non-rectangular domains. Singularities, which may appear in the expression of stress components or boundary conditions at a degenerated point of the grid, are removed by means of the Taylor expansion. The results of three examples are compared with the exact solutions. It is shown that accurate results can be achieved by the DQM. In addition, three geometric transformations are conducted in the third example so that the effect of mapping on the convergence and accuracy of results is investigated. It is found that rapid convergence can be fulfilled if the degenerated point of the mesh falls on a Dirichlet boundary. The approach addressed in the paper can be extended to other potential problems governed by either the Poisson equation or the Laplace equation. © 1998 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Some modified AGE methods for the convection–diffusion equation are developed in this paper. Firstly, there is a treatment on the convection term in the equation which is different from that in the AGE method by Evans and Abdullah (1985). Secondly, upwind-type schemes are used for the convection dominated diffusion problems. All the modified AGE methods in the paper are unconditionally stable. The numerical example is given to show the effectiveness of the methods. The methods have the obvious property of parallelism. © 1998 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Recent work has shown that many ceramic fibres which are increasingly used to line industrial furnaces have highly spectral-dependent emissivities. This paper presents an extension to the standard zone method for radiative heat transfer calculations which directly models spectral variation in surface and gas properties. A short description of the zone method is given along with a summary of the weighted sum of grey gases model. This is often used as a means of representing the temperature dependence of total gas properties brought about because of the spectral non-uniformity of these properties. When surfaces as well as the gas are non-grey, a new approach is required. The method of this paper is based on dividing the spectrum into a number of bands and treating the properties as constant within each band. This method can be used directly if the boundary conditions specify all the zone temperatures. However, if some temperatures are unknown, then an iterative solution technique is required. Results of some sample calculations are presented. These illustrate the importance of directly modelling the spectral behaviour of gas and surface properties. © 1997 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper demonstrates a simple finite element implementation of Lagrange multipliers to model the mechanical behaviour of an orthotropic composite material. The research shows the proper set of kinematic boundary conditions that must be applied in 2D plane stress elasticity to achieve the correct unit strain vectors that, upon interrogation of the associated Lagrange multipliers, give the stresses induced by these strain vectors. From these stresses the terms in the elasticity matrix can be evaluated. As well as demonstrating the correct kinematic conditions required, the paper presents the consequences of applying intuitive but incorrect conditions. © 1997 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper treats a united-form solution for a point force applied at the interior of an infinite transversely isotropic solid. Several heuristic functions are adopted to obtain the expressions of the solution based on the general solution. To exclude some indeterminate attributes, the expressions are rewritten. In the final expressions, unlike previous publications where the solutions are expressed in different forms, or when some individual constants have different definitions depending on the conditions satisfied by the elastic constants, we provide united solutions which are suitable for all stable transversely isotropic materials and isotropic materials. Thus accurate numerical evaluation of the boundary element method can be performed directly without the need to resolve the singularity algebraically. Some numerical examples with BEM are also presented in this paper. © 1997 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents an exact structural static reanalysis method for locally modified structures. Through the introduction of structural rigid body motion eigenvectors, the generalized structural compliance matrix can be obtained and the original stiffness equation is transformed into a linear system of much lower order. The general solution of displacements can be expressed prior to any assignment of boundary conditions. For a structure with given boundary and loading conditions, the displacements can be obtained by solving this linear system. For locally modified structures, the structural compliance matrix can be adjusted quickly. This static reanalysis method can be used for structures with modifications on structural elements, boundary and loading conditions, either independently or in combination. Two test examples are provided in the paper to prove the efficiency of the method. © 1997 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents an exponentially fitted finite difference scheme of order one for the singularly peturbed Riccati equation εu′ (t) = c(t)u2(t) + d(t)u(t) + e(t), t>0, u(0) = φ with a small parameter ε multiplying the first derivative. The scheme is a modified form of Carroll's scheme (1986). The scheme is both optimal and uniform with respect to the small parameter ε, that is, the solution of the difference scheme satisfies error estimates of the form | u(ti) - ui | ≤ C min(h,ε) where C is independent of i, h and ε. Here h is the mesh size and ti is any mesh point. The scheme is explicit in nature and so no iteration is involved for the convergence of the solution. The scheme presented in this paper is new and it is different from the uniform schemes of order one available in the literature. Finally, numerical experimetns are presented. [ABSTRACT FROM AUTHOR]

In the paper the simulation of incompressible flow in 2D by the least-squares finite element method (LSFEM) in the velocity -- vorticity -- pressure version is studied. A problem with this method is that it does not conserve mass exactly, i.e. div uh ≠ 0 exactly. In the paper a modified LSFEM is developed which enforces a near zero residual of mass conservation, i.e. div u is nearly zero at every point of the discretization. This is accomplished by adding an extra restriction in the divergence free equation through the Lagrange multiplier strategy. [ABSTRACT FROM AUTHOR]

In the paper a semi-analytic approach for solving dynamic response problems is developed which is based on Gurtin's convolution-type variational principle. A finite element discretization in the space domain and a series representation in the time domain are considered. This approach overcomes the shortcomings of existing methods yet utilizes their advantages for solving dynamic response problems. The example of a beam shows that this new approach is a very effective method in obtaining solutions for dynamic response problems. The paper also concentrates on utilizing time domain series for various boundary conditions, so that solutions calculated by this approach have a very high accuracy and efficiency. [ABSTRACT FROM AUTHOR]

The paper presents finite difference schemes of order two for stiff initial-value problems, with a small parameter ∊ multiplying the first derivative. The schemes are a modified form of the classical trapezoidal rule. They are both optimal and uniform with respect to the small parameter ∊, that is, the solution of the difference schemes satisfies error estimates of the form | u(ti)-ui| ⩽ C min(h²,∊) where C is independent of i, h and ∊. Here h is the mesh size and ti is any mesh point. The schemes presented in this paper are different from the scheme of order two available in the literature. Finally, numerical experiments are presented. [ABSTRACT FROM AUTHOR]

The paper presents a new method for the numerical solution of transient linear heat conduction problems. In the proposed method, the transient linear heat conduction equation is first integrated with respect to time over subsequent intervals. Then the resulting set of elliptic equations is discretized in space according to a finite-element procedure. The method is unconditionally stable. At the end of the paper, the effectiveness of the proposed method is assessed through some numerical examples. [ABSTRACT FROM AUTHOR]

In a recent paper we presented a data structure to be used with multigrid techniques on non- homogeneously refined FEM meshes. This paper focuses on the adaptive refinement techniques used there. The error estimate is obtained from standard Taylor series. For each element we compute its efficiency in terms of the size, the norm of the second derivatives of the unknown and the parameter p, where Lp is the chosen norm. The way the norm influences the optimal mesh is studied. The number of elements to be refined at each step is such to produce a fast convergence to the optimal mesh, followed by successive homogeneous refinements. We hope that the analysis of these two subjects could be of value for people working with other (perhaps very dissimilar) adaptive refinement techniques (error estimate and data structure, for instance). [ABSTRACT FROM AUTHOR]

A number of improved finite-difference solutions of explicit form have been reported recently. The choice of a particular solution of these improved explicit forms is dependent on the value of the non-dimensional time step as well as whether the process involves cooling or heating. The conditions for stable operation are clarified in the paper. Two new improved solutions of implicit forms are also reported in the paper. These new solutions give better accuracy compared to the conventional Crank-Nicolson and pure implicit methods, and have unrestricted stability. [ABSTRACT FROM AUTHOR]

The virtual contact loading method (VCLM), a highly efficient numerical method to solve elastic contact problems, is proposed in this paper. Having applied virtual loads on the possible contact region (PCR) of a structure system, we carried out the usual finite-element calculations only once and made a local iteration analysis in PCR then the contact region (shape and size), contact state (stick, slide or mixed), contact normal and shear stress distributions, and the stress and displacement fields in contact bodies were all obtained simultaneously. This method is very simple and easy to use. The elastic contact problems for cylinder-cylinder are solved in this paper and the results agree well with those in previous work. [ABSTRACT FROM AUTHOR]

This paper examines the suitability of three-dimensional finite elements to model accurately problems involving material incompressibility, using the displacement finite element method and exact numerical integration. The previously used method for classification of element suitability is presented and extended to the three-dimensional case. However, an alternative approach for examining suitability, quantified in terms of free degrees of freedom (equal to the degrees of freedom minus the incompressibility constraints), is introduced. This is used to examine Lagrangian cubic, serendipity cubic and tetrahedral three-dimensional elements configured in a regular cubic arrangement. The findings of this paper are substantiated by a number of three-dimensional numerical experiments and comparison with a separate two-dimensional study. All serendipity cubic elements are found to be unsuitable. The linear strain tetrahedron is on the borderline of suitability in a 6-tetrahedra-per-cube arrangement, and is thought to be only suitable if the mesh boundary nodes are not over-constrained. The same element in a 5-tetrahedra-per-cube arrangement, and higher order tetrahedra (quadratic strain etc), are suitable. The Lagrangian cube elements of higher order than the 27-node cube are suitable, but are probably not as efficient computationally as the tetrahedral elements of the same order. [ABSTRACT FROM AUTHOR]

In this paper, the homotopy perturbation method is used to implement the nonlinear Korteweg–de Vries equation. The analytical solution of the equation is calculated in the form of a convergent power series with easily computable components. A suitable choice of an initial solution can lead to the needed exact solution by a few iterations. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In a recent paper, the weighted essentially non-oscillatory (WENO) numerical scheme was applied to solve a multi-class Lighthill–Whitham–Richards (MCLWR) traffic flow model (J. Comput. Phys. 2003; 191:639–659). We discuss and present an enhanced WENO scheme with Lax–Friedrichs flux splitting by improving the estimation of the minimal characteristic speed of the MCLWR model, which is based on a set of inequalities of eigenvalues. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper an efficient method is developed for the formation of null bases of finite element models (FEMs) consisting of rectangular plane stress and plane strain elements, corresponding to highly sparse and banded flexibility matrices. This is achieved by associating special graphs with the FEM and selecting appropriate subgraphs and forming the self-stress systems on these subgraphs. The efficiency of the present method is illustrated through three examples. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Our target is to develop computational techniques for studying aerodynamic interactions between multiple objects. The computational challenge is to predict the dynamic behavior and path of the object, so that separation (the process of objects relatively falling or moving away from each other) is safe and effective. This is a very complex problem because it has an unsteady, 3D nature and requires the solution of complex equations that govern the fluid dynamics (FD) of the object and the aircraft together, with their relative positions changing in time. Large-scale 3D FD simulations require a high computational cost. Not only must one solve the time-dependent Navier–Stokes equations governing the fluid flow, but also one must handle the equations of motion of the object as well as the treatment of the moving domain usually treated as a type of pseudo-solid. These costs include mesh update methods, distortion-limiting techniques, and remeshing and projection tactics. To save computational costs, point force calculations have been performed in the past. This paper presents a hybrid between full mesh-moving simulations and the point force calculation. This mesh-moving alternative is called FOIST: fluid–object subcomputation interaction technique. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Circular plates are important structural elements in modern engineering structures. In this paper a computationally efficient and accurate numerical model is presented for the study of free vibration and bending behavior of thick circular plates based on Mindlin plate theory. The approach developed is based on the discrete singular convolution method and the use of regularized Shannon's delta kernel. Frequency parameters, deflections and bending moments are obtained for different geometric parameters of the circular plate. Comparisons are made with existing numerical and analytical solutions in the literature. It is found that the DSC method yields accurate results for the free vibration and bending problems of thick circular plates. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

When solving parabolic partial differential equations using finite difference non-overlapping domain decomposition methods, one often uses the stripwise decomposition of spatial domain and it can be extended to the rectangular decomposition without further analysis. In this paper, we analyze the rectangular decomposition when the modified implicit prediction (MIP) algorithm is used. We show that the performance of the rectangular decomposition and the stripwise decomposition is different. We compare spectral radius, maximum error, efficiency, and total operations of the rectangular and the stripwise decompositions. We investigate the accuracy of the interface of the rectangular decomposition and the effects of the correction phase of the rectangular decomposition. Numerical experiments have been done in both two and three spatial dimensions and show that the rectangular decomposition is not better than the stripwise decomposition. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Molecular imaging possesses the ability to characterize and measure biological processes at the cellular and molecular level in vivo. As one of the new molecular imaging modalities, bioluminescence tomography (BLT) is to reconstruct the light distribution inside a small animal from the photon flux measured on its surface. To obtain accurate and robust reconstruction, it needs a good understanding of the propagation of photons in biological tissues, which is referred to as the forward problem in BLT. Because the turbid media is high scattering and low absorption, the propagation process can be described by the steady diffusion equation. In this paper, an hp-adaptivity method for BLT forward problem is presented based on finite elements of high orders and moderate meshes by finite element method (FEM). Both numerical simulation and physical experiment are performed to evaluate the accuracy of solution and the efficiency of computation. The relevant results show that element order is more critical than mesh size to produce an accurate FEM solution efficiently. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Most finite element (FE) software uses numerical integration to compute FE stiffness matrices. In the case of straight-sided isoparametric triangular elements, numerical integration is exact, provided a sufficient number of integration points are used. In this paper, the same integrations are performed analytically in closed form with the help of computer algebra software for 3-, 6-, 10- and 15-noded triangles. The resulting analytical expressions have been converted into Fortran 95 subroutines and compared with the conventional numerical integration methods. The analytical routines produce exactly the same results as their numerical counterparts, but run significantly faster. All Fortran 95 code developed in this study is available on the first author's Web site. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a two-dimensional frequency domain model for analyzing resonant structures. In this model, the transverse waves in the waveguide cross-section at any point are simulated by superposition of two waves in two perpendicular directions. The relationships between the physical wave parameters and the model parameters are derived. Results for cutoff wave numbers of homogeneous arbitrarily shaped cylindrical waveguides are given to test the validity of the model. These results are compared with available analytical solutions and results given by other published methods. The model proves to give good treatment for boundary conditions and accurate results with smaller matrix size in comparison with other numerical methods. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper concerns the shell element formulation used for linear analysis. Introduction of hierarchical incompatible modes into the ordinary 8-node solid element is very effective to obtain the rational deflection–rotation relationship. An efficient revision scheme without using numerical volume integration is developed to ensure the satisfaction of the patch test. A lot of numerical tests are carried out for the validation of the present element. Numerical results show that the element can give satisfactory accuracy and convergence, especially for moderately thick shells. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]